1. Field of the Invention
The present invention relates to a hub clutch device, and more particularly to a hub clutch device for a bicycle.
2. Description of the Related Art
A conventional hub clutch device for a bicycle in accordance with the prior art shown in FIGS. 6 and 7 comprises a threaded shaft 601, a hub 60 rotatably mounted on the shaft 601 for mounting a wheel (not shown) and having an inner wall formed with a recess 602, a guide sleeve 65 mounted on the shaft 601 and located between two bearings 61 and 66, a fixed clutch 64 mounted on the guide sleeve 65 and having a plurality of ratchet teeth 641, a fixing seat 67 secured on the fixed clutch 64 to rotate the fixed clutch 64, a freewheel (not shown) mounted on the fixing seat 67 to rotate the fixing seat 67, a movable clutch 63 mounted on the guide sleeve 65 and having a plurality of ratchet teeth 631 meshing with the ratchet teeth 641 of the fixed clutch 64, and a spring 62 mounted on the guide sleeve 65 and biased between the movable clutch 63 and the hub 60.
In operation, when a pedal (not shown) of the bicycle is stepped, a chainwheel (not shown) is rotated to rotate a chain (not shown) which rotates the freewheel which rotates the fixing seat 67 which rotates the fixed clutch 64 which rotates the movable clutch 63 by engagement of the ratchet teeth 631 and 641. In such a manner, the movable clutch 63 is secured in the hub 60 so that the hub 60 is driven by the movable clutch 63 to rotate.
When the pedal stops operating, the freewheel stops rotating, so that the force applied on the fixing seat 67 is removed. At this time, the movable clutch 63 and the hub 60 are still rotated with the wheel. Thus, when the velocity of the fixing seat 67 and the fixed clutch 64 is smaller than that of the movable clutch 63 and the hub 60, the ratchet teeth 631 of the movable clutch 63 bias the spring 62 to disengage and pass through the ratchet teeth 641 of the fixed clutch 64, so as to detach the movable clutch 63 from the fixed clutch 64. Thus, when the movable clutch 63 and the hub 60 are rotated, the fixing seat 67 and the fixed clutch 64 are not rotated, so that the freewheel will not be rotated by the wheel when the pedal stops operating.
However, noise is produced when the ratchet teeth 631 of the movable clutch 63 pass through the ratchet teeth 641 of the fixed clutch 64, thereby producing noise when the wheel idles. In addition, it is necessary to have a precise fit between the ratchet teeth 631 of the movable clutch 63 and the ratchet teeth 641 of the fixed clutch 64, thereby increasing costs of fabrication.